I got a p0420 code and replaced my cat. Now the car runs fine and passed the smog. But, the old cat was totally hollow, seems like everything just evaporated...! Do you guys think that there might be som'n wrong with the engine? can it be too much heat??? would it void the warrenty on my new cat????

the engine usually runs <200 degrees..!

thanx..!

 

Haha hollowing your cat is something called a "free mod" meaning a previous owner took it off and hollowed it out.
Hollowing your cat won't give the driver noticable gains unless there cat was clogged up. It will however change the sound of the exhaust making it more poppy and raspy.
This sometimes will through off a code if you have OBDII (rear O2 sensor), in which case you can purchase an O2 simulator or have your PCM tuned to delete it.
However if you have to pass a "sniffer test" its not a good idea, but if you have no test or just a visual test theres nothing holding you back.

 

To sum it up you have nothing to worry about.

 

+1 on what Clyon said, But
It is possible that the Cat fell apart on its own. I have seen it a few times. Its more likely to happen from bottoming out on the cat then overheating it. On a side note if you are 100% sure the cat was not hollowed out by someone that means most of your cat now resides in your muffler. That can cause problems down the road with exhause flow.

 

omg stupid me....!! lol

well still is there anyway to make sure its not the heat that caused the thing?